Three-dimensional imaging method and device based on multi-angle track

Abstract

The invention belongs to the technical field of three-dimensional imaging, and relates to a three-dimensional imaging method and device based on a multi-angle track. The method comprises the following steps: acquiring a two-dimensional image of radio equipment, and obtaining slant range-azimuth two-dimensional SAR images of a target under different visual angles of a current track; the slope distance-azimuth two-dimensional SAR image is converted into a height-azimuth two-dimensional SAR image; converting the height-azimuth two-dimensional SAR image in the original coordinate system into a height-azimuth two-dimensional SAR image in a reference coordinate system, and taking the height-azimuth two-dimensional SAR image as an echo; stacking echoes of the radio equipment at the same height under different visual angles to obtain slices at the corresponding height; stacking the slices with different heights to obtain three-dimensional information of the target under the current track; and projecting the three-dimensional information of the target under the plurality of tracks to a reference coordinate system to obtain a three-dimensional image of the target. According to the invention, three-dimensional imaging can be rapidly and accurately carried out in a local area, and the simplicity and the calculation efficiency of an algorithm are maintained at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of three-dimensional imaging, and in particular to a three-dimensional imaging method and device based on multi-angle trajectories. Background Art

[0002] With the rapid development of science and technology, 3D imaging technology has become an indispensable part of modern industry, scientific research and daily life. From medical imaging to geographic information systems (GIS) to sensor systems for self-driving cars, 3D imaging technology has a wide range of applications and its importance is becoming increasingly prominent. Among the many 3D imaging technologies, imaging methods based on radio equipment have attracted much attention due to their advantages such as being able to penetrate a variety of materials, being unrestricted by light conditions, and being able to provide real-time dynamic information.

[0003] The current three-dimensional SAR imaging technologies mainly include: Multi-Baseline SAR (MBSAR) technology, Circular SAR (CSAR) technology, Holographic Synthetic Aperture Radar (HoloSAR) technology, Curvi Linear SAR (CLSAR) technology and Linear Array Synthetic Aperture Radar (LASAR) technology.

[0004] Tomographic SAR technology is an information inversion technology developed on the basis of Interferometric Synthetic Aperture Radar (InSAR). However, in order to ensure high resolution and imaging accuracy in elevation, more flyby data is required, and multi-baseline tomographic SAR imaging is generally obtained by repeated flyby, which is expensive.

[0005] Circular SAR technology is to obtain 360° all-round 3D scattering information of the observation area by making a circular motion around the observation area. Its imaging principle relies on the circular motion trajectory, through which all-round information of the target is obtained and 3D image reconstruction is realized. Although CSAR can obtain sub-wavelength resolution in the range-azimuth plane, the limitation of effective bandwidth in elevation leads to very low resolution in elevation, which seriously limits the practical engineering application of single-circle CSAR 3D imaging.

[0006] Holographic SAR technology is a special form of multi-baseline SAR. It solves the overlap problem of anisotropic targets while observing in all directions. HoloSAR uses multiple motion trajectories (i.e., multiple baselines) to obtain three-dimensional information of the target. These baselines can be circular trajectories at different heights or angles. This imaging technology requires the radio equipment platform to be able to continuously observe the target at 360° from different heights. This all-round observation trajectory is suitable for airborne platforms, but the system complexity is high in implementation. In addition, the observation equation of holographic SAR may become larger or even a huge equation due to the increase in dimensions and integrity requirements. This brings theoretical problems of feasibility and convergence of the solution, as well as problems of efficient engineering implementation.

[0007] Curvilinear SAR technology sets the flight path of a moving platform in three-dimensional space, and uses the non-linear motion of the moving platform trajectory to synthesize a virtual sparse array to reconstruct the three-dimensional information of the scene. In order to obtain better parameter estimation performance, CLSAR needs to place higher requirements on the curved trajectory of the platform. For example, large apertures and more complex apertures with higher nonlinearity are more conducive to forming a dense data acquisition set, thereby improving the estimation accuracy of parameters. However, due to the limitations of the platform's flight performance and from a safety perspective, overly complex trajectories are unrealistic.

[0008] Linear array SAR technology is to fix a linear array antenna on the wing of the aircraft, and use the linear array antenna placed in a tangent track and the linear motion of the platform to synthesize a virtual array to reconstruct the three-dimensional information of the scene. However, the linear array three-dimensional SAR imaging algorithm is affected by the Nyquist sampling theorem and the array grating lobe, requiring the array elements to be evenly distributed and the array element spacing to be as small as possible, which leads to too many array elements, and the traditional algorithm has a high side lobe of the cross-heading resolution function. At the same time, it is limited by the Rayleigh limit, resulting in a decrease in system resolution.

[0009] In summary, traditional 3D imaging methods often rely on complex algorithms and hardware with high computational costs (for example, there are limitations in data acquisition, requiring specific flight conditions and trajectories, which is a challenge for actual operation; existing 3D SAR systems are often large and heavy, which limits their application on more platforms, especially in situations where there are strict requirements on device size and weight; their system complexity is high, the development is difficult, and the system miniaturization and application promotion are difficult; the data volume is huge, the processing process is complex, and the target imaging resolution is low, resulting in reduced accuracy and reliability of imaging results). For current SAR systems, this limits their feasibility in real-time applications and in a wider range of fields; in addition, for large-scale or dynamically changing scenes, traditional centralized radio systems may find it difficult to provide sufficient coverage and flexibility. In other words, traditional SAR 3D technology often faces problems such as high cost, low elevation resolution, low timeliness, complex track, and low imaging quality. Summary of the invention

[0010] Based on this, it is necessary to provide a three-dimensional imaging method and device based on multi-angle trajectories to address the above-mentioned technical problems, which can quickly and accurately perform three-dimensional imaging in a local area while maintaining the simplicity and computational efficiency of the algorithm, and can also provide sufficient coverage and flexibility for large-scale or dynamically changing scenes.

[0011] A three-dimensional imaging method based on multi-angle trajectories, comprising: Acquire a two-dimensional image of the radio equipment and use a back-projection algorithm to obtain a two-dimensional SAR image of the target in slant range and azimuth at different viewing angles of the current trajectory; According to the imaging plane center slant distance at different viewing angles, the angle between the radio equipment and the imaging plane center slant distance is obtained; according to the angle, the slant range-azimuth two-dimensional SAR image is converted into an altitude-azimuth two-dimensional SAR image; Obtaining the angles between different radio devices and the reference coordinate axis, calculating the coordinate axis transformation matrix and the translation matrix, so as to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo; Take the echoes of the same height under different viewing angles of the radio equipment and stack them to obtain slices at the corresponding height; take slices at different heights and stack them to obtain the three-dimensional information of the target under the current trajectory; The three-dimensional information of the target under multiple trajectories is projected onto the reference coordinate system to obtain a three-dimensional image of the target.

[0012] In one embodiment, the slant range-azimuth two-dimensional SAR images of the target at different viewing angles of the current trajectory include:

[0013] In the formula, For radio equipment a Slant range-azimuth two-dimensional SAR image under viewing angle, for a The complex scattering coefficient under viewing angle, is the impulse response in the slant range direction, For radio equipment a Slant range coordinates under viewing angle, To target radio equipment a Slant distance under viewing angle, is the impulse response in azimuth, For radio equipment a The azimuth coordinates under the viewing angle, For radio equipment a The target position under the viewing angle, is an imaginary unit, is the wavelength of radio equipment;

[0014] In the formula, For radio equipment b Slant range-azimuth two-dimensional SAR image under viewing angle, for b The complex scattering coefficient under viewing angle, For radio equipment b Slant range coordinates under viewing angle, To target radio equipment b Slant distance under viewing angle, For radio equipment b The azimuth coordinates under the viewing angle, For radio equipment b The target position in the viewing angle.

[0015] In one embodiment, obtaining the angle between the radio device and the center slant distance of the imaging plane according to the center slant distance of the imaging plane at different viewing angles includes:

[0016]

[0017]

[0018]

[0019] In the formula, is the target height position, For radio equipment a The angle between the viewing angle and the slant distance from the center of the imaging plane, For radio equipment b The angle between the viewing angle and the slant distance from the center of the imaging plane.

[0020] In one embodiment, according to the angle, converting the slant range-azimuth two-dimensional SAR image into the altitude-azimuth two-dimensional SAR image includes: When the target meets the far-field condition:

[0021]

[0022] but:

[0023] We can get:

[0024]

[0025] In the formula, is the error between the target height and the estimated value when the target is not in the center of the imaging plane, For radio equipment a Two-dimensional SAR image in altitude-azimuth direction under viewing angle, is the height coordinate, For radio equipment b Altitude-azimuth two-dimensional SAR image under viewing angle.

[0026] In one embodiment, the angles between different radio devices and the reference coordinate axis are obtained, and the coordinate axis transformation matrix and the translation matrix are calculated to convert the altitude-azimuth two-dimensional SAR image in the original coordinate system into the altitude-azimuth two-dimensional SAR image in the reference coordinate system as the echo, including: Obtain the angles between different radio devices and the reference coordinate axis, and calculate the coordinate axis transformation matrix according to the basis transformation principle; Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system; According to the coordinate axis transformation matrix and the translation matrix, the axis shift formula is used to transform the altitude-azimuth two-dimensional SAR image in the original coordinate system into the altitude-azimuth two-dimensional SAR image in the reference coordinate system, and the altitude-azimuth two-dimensional SAR image in the reference coordinate system is used as the echo. In one embodiment, the angles between different radio devices and the reference coordinate axis are obtained, and the coordinate axis transformation matrix is ​​calculated according to the basis transformation principle, including:

[0027] In the formula, is the axis transformation matrix, is the angle between different radio devices and the reference coordinate axis.

[0028] In one embodiment, the geometric relationship between the coordinate axis transformation matrix and the translation matrix is ​​obtained, and the translation matrix is ​​calculated by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system, including:

[0029]

[0030]

[0031] In the formula, is the position of the image origin projected to the reference coordinate system, is the position of the target in the original coordinate system, is the position of the target in the reference coordinate system, is the translation matrix, Project the image origin to the reference coordinate system The position of the direction, is the image origin in the reference coordinate system The location of the direction.

[0032] In one embodiment, the altitude-azimuth two-dimensional SAR image in the reference coordinate system includes:

[0033]

[0034] In the formula, For radio equipment a The reference coordinate system height-azimuth two-dimensional SAR image under the viewing angle, For Select the first indivual, is half of the total number of slices in height, For the A height slice, For radio equipment b Two-dimensional SAR image in the height-azimuth direction of the reference coordinate system under viewing angle.

[0035] In one embodiment, stacking echoes at the same height under different viewing angles of the radio device to obtain slices at corresponding heights includes:

[0036] In the formula, is the slice at the corresponding height.

[0037] A three-dimensional imaging device based on multi-angle trajectories, comprising: An acquisition module is used to acquire a two-dimensional image of the radio equipment and use a back-projection algorithm to obtain a slant range-azimuth two-dimensional SAR image of the target at different viewing angles of the current trajectory; A conversion module is used to obtain the angle between the radio equipment and the center slant distance of the imaging plane according to the center slant distance of the imaging plane at different viewing angles; and convert the slant range-azimuth two-dimensional SAR image into an altitude-azimuth two-dimensional SAR image according to the angle; The echo module is used to obtain the angles between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and the translation matrix, so as to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo; The stacking module is used to stack the echoes at the same height under different viewing angles of the radio equipment to obtain slices at the corresponding height; and to stack slices at different heights to obtain the three-dimensional information of the target under the current track; The projection module is used to project the three-dimensional information of the target under multiple trajectories onto the reference coordinate system to obtain a three-dimensional image of the target.

[0038] The above-mentioned three-dimensional imaging method and device based on multi-angle trajectory have the following beneficial effects: 1) The importance of local area imaging is taken into account, allowing users to flexibly select the size of the imaging area according to the error curve to adapt to different application scenarios and accuracy requirements; in addition, a distributed radio equipment configuration is adopted, which is not restricted by fixed geometric shapes and can be arbitrarily configured according to actual needs, thereby providing greater flexibility and adaptability; through the selection of local areas and the deployment of distributed radio equipment, this method can significantly improve the imaging speed and efficiency while ensuring imaging accuracy, which is particularly important for application scenarios that require rapid response. For example, in the fields of emergency rescue, environmental monitoring or traffic management, fast and accurate three-dimensional imaging capabilities can greatly improve decision-making efficiency and response speed.

[0039] 2) Only two lines at any angle can be used for imaging, unlike the existing technology which requires at least a surface for imaging. This simplifies the imaging process and improves the imaging speed while ensuring the imaging quality, thus achieving fast data processing and imaging. It not only reduces the demand for computing resources and reduces computing costs, but also makes the entire imaging process more efficient, effectively solving the problems of low imaging speed and high cost in three-dimensional imaging. It has great application value and broad application prospects in actual engineering, and is particularly suitable for application scenarios that require real-time or near real-time feedback, such as rapid deployment and dynamic monitoring of drone swarms.

[0040] 3) The three-dimensional imaging method of this application is particularly suitable for drone swarms. The configuration of the drone swarm can be arbitrarily and flexibly configured according to the mission requirements. Whether it is a linear, grid-shaped or arbitrarily shaped flight formation, it can effectively collect three-dimensional data. The arbitrariness of this configuration provides great flexibility for the deployment of drone swarms, enabling them to adapt to various complex terrains and environmental conditions, while improving the coverage and efficiency of data collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1A schematic diagram of a flow chart of a three-dimensional imaging method based on multi-angle trajectories in one embodiment; Figure 2 A schematic diagram of a radio device configuration in one embodiment; Figure 3 A schematic diagram of basis transformation and translation transformation in one embodiment; Figure 4 A schematic diagram of a height slice in one embodiment; Figure 5 It is a schematic diagram of projection of a target at various heights in one embodiment; Figure 6 For one embodiment of a radio device a Slant range-azimuth two-dimensional SAR image obtained by viewing angle; Figure 7 For one embodiment of a radio device b Slant range-azimuth two-dimensional SAR image obtained by viewing angle; Figure 8 For one embodiment of a radio device a The altitude-azimuth two-dimensional SAR image obtained by viewing angle; Fig. 9 For one embodiment of a radio device b The altitude-azimuth two-dimensional SAR image obtained by viewing angle; Fig.10 For one embodiment of a radio device a , b The same height is obtained by slicing down through the basis transformation and translation transformation x - y Directional 2D SAR images; Fig.11 For one embodiment of a radio device a , b A top view of the obtained target three-dimensional imaging result; Fig.12 For one embodiment of a radio device a , b The obtained front view of the target three-dimensional result; Fig.13 In one embodiment Fig.12 Target x Slice diagram of direction; Fig.14 In one embodiment Fig.12 Target y Slice diagram of direction; Fig.15 In one embodiment Fig.12 Target z Slice diagram of direction; Fig.16 For one embodiment of a radio device a , b , c The target three-dimensional result map obtained; Fig.17 In one embodiment Fig.16 Target x Slice diagram of direction; Fig.18 In one embodiment Fig.16 Target y Slice diagram of direction; Fig.19 In one embodiment Fig.16 Target z Slice diagram of direction; Fig. 20 The structure block diagram of a three-dimensional imaging device based on multi-angle trajectory in one embodiment. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0043] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, etc., unless otherwise clearly and specifically defined.

[0044] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0045] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0046] This application provides a three-dimensional imaging based on multi-angle trajectory, such as Figure 1 The flowchart shown, in one embodiment, includes: Step 101, obtain a two-dimensional image of the radio equipment, and use a back-projection algorithm to obtain a slant range-azimuth two-dimensional SAR image of the target at different viewing angles of the current trajectory.

[0047] Specifically, the slant range-azimuth two-dimensional SAR images of the target at different viewing angles of the current trajectory include:

[0048] In the formula, For radio equipment a Slant range-azimuth two-dimensional SAR image under viewing angle, for a The complex scattering coefficient under viewing angle, is the impulse response in the slant range direction, For radio equipment a Slant range coordinates under viewing angle, To target radio equipment a Slope range under viewing angle (also the slant range position of target P), is the impulse response in azimuth, For radio equipment a The azimuth coordinates under the viewing angle, For radio equipment a The target position under the viewing angle, is an imaginary unit, is the wavelength of radio equipment;

[0049] In the formula, For radio equipment b Slant range-azimuth two-dimensional SAR image under viewing angle, for b The complex scattering coefficient under viewing angle, For radio equipment b Slant range coordinates under viewing angle, To target radio equipment b Slope distance under viewing angle, For radio equipment b The azimuth coordinates under the viewing angle, For radio equipment b The target position in the viewing angle.

[0050] In this step, if Figure 2 As shown, I is the imaging plane, W is the side length of the imaging plane, is the angle between different radio devices and the reference coordinate axis, For radio equipment a The angle between the viewing angle and the slant distance from the center of the imaging plane (also the angle of incidence at different viewing angles), For radio equipment b The angle between the viewing angle and the slant distance from the center of the imaging plane, the azimuth coordinate of the radio equipment a It can be expressed as y .

[0051] The radio device may be a radar.

[0052] As for how to obtain a two-dimensional image of a radio device and a back projection algorithm, these are existing technologies and will not be described in detail here.

[0053] Step 102, obtaining the angle between the radio equipment and the center slant distance of the imaging plane according to the center slant distance of the imaging plane at different viewing angles; and converting the slant range-azimuth two-dimensional SAR image into an altitude-azimuth two-dimensional SAR image according to the angle.

[0054] Specifically: According to the slant distance of the imaging plane center at different viewing angles, the angle between the radio equipment and the slant distance of the imaging plane center is obtained:

[0055]

[0056]

[0057]

[0058] In the formula, is the target height position, For radio equipment a The angle between the viewing angle and the slant distance from the center of the imaging plane (also the angle of incidence at different viewing angles), For radio equipment b The angle between the viewing angle and the slant distance from the center of the imaging plane; According to the angle between the radio equipment and the slant range of the imaging plane center, the slant range-azimuth 2D SAR image is converted into an altitude-azimuth 2D SAR image: When the target meets the far-field condition:

[0059]

[0060] but:

[0061] We can get:

[0062]

[0063] In the formula, is the error between the target height and the estimated value when the target is not in the center of the imaging plane, For radio equipment a Two-dimensional SAR image in altitude-azimuth direction under viewing angle, is the height coordinate, For radio equipment b Altitude-azimuth two-dimensional SAR image under viewing angle.

[0064] In this step, the current coordinate system of the target is generally an oblique coordinate system.

[0065] Step 103, obtaining the angles between different radio devices and the reference coordinate axis, calculating the coordinate axis transformation matrix and the translation matrix, so as to transform the altitude-azimuth two-dimensional SAR image in the original coordinate system into the altitude-azimuth two-dimensional SAR image in the reference coordinate system as the echo.

[0066] Specifically: Obtain the angles between different radio devices and the reference coordinate axis, and calculate the coordinate axis transformation matrix according to the basis transformation principle; Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system; According to the coordinate axis transformation matrix and the translation matrix, the axis shift formula is used to transform the altitude-azimuth two-dimensional SAR image in the original coordinate system into the altitude-azimuth two-dimensional SAR image in the reference coordinate system, and the altitude-azimuth two-dimensional SAR image in the reference coordinate system is used as the echo.

[0067] More specifically: Get the angles between different radio devices and the reference coordinate axis, and calculate the coordinate axis transformation matrix based on the basis transformation principle:

[0068] In the formula, is the axis transformation matrix, is the angle between different radio devices and the reference coordinate axis; like Figure 3 As shown, get the geometric relationship between the coordinate axis transformation matrix and the translation matrix:

[0069] Combined with the relationship between the original coordinate system and the reference coordinate system (also the relationship between the coordinate system basis and the rectangular coordinate system basis):

[0070] And combined with the coordinate axis transformation matrix, calculate the translation matrix:

[0071] In the formula, is the position of the image origin projected to the reference coordinate system, is the position of the target in the original coordinate system, is the position of the target in the reference coordinate system, is the translation matrix, Project the image origin to the reference coordinate system The position of the direction, is the image origin in the reference coordinate system Direction location; According to the coordinate axis transformation matrix and the translation matrix, the axis shift formula is used to transform the height-azimuth 2D SAR image in the original coordinate system into the height-azimuth 2D SAR image in the reference coordinate system, and the height-azimuth 2D SAR image in the reference coordinate system is used as the echo:

[0072]

[0073] In the formula, For radio equipment a The reference coordinate system height-azimuth two-dimensional SAR image under the viewing angle, For Select the first The total number of height slices is indivual, is half of the total number of slices in height, For the A height slice, For radio equipment b Two-dimensional SAR image in the height-azimuth direction of the reference coordinate system under viewing angle.

[0074] In this step, the original coordinate system is the oblique coordinate system, and the reference coordinate system is the rectangular coordinate system.

[0075] because The influence of causes a translation when transforming the oblique coordinate system into the reference coordinate system. The new basis vectors are rotated or scaled relative to the old basis vectors. Then, in the reference coordinate system, the point that was originally at the origin in the original coordinate system may no longer be at the origin.

[0076] As for the basis transformation principle and the axis shift formula, they are existing technologies and will not be described in detail here.

[0077] Step 104 , stacking the echoes at the same height under different viewing angles of the radio device to obtain slices at the corresponding height; stacking the slices at different heights to obtain the three-dimensional information of the target under the current trajectory.

[0078] Specifically: Take the echoes of the same height from different viewing angles of the radio equipment and stack them to get the slices at the corresponding height:

[0079] In the formula, is the slice at the corresponding height; Slices at different heights are stacked to obtain the three-dimensional information of the target under the current trajectory.

[0080] In this step, the projection theorem is used to reconstruct the target two-dimensional coordinate information from different slices (a slice at the same height is a picture, which is a radio device a Slices of perspective and b The target’s height information (i.e., the target’s three-dimensional information) is obtained by continuously stacking the slices in the height direction, such as Figure 4 and Figure 5 As shown, XOZ is a radio device b Projection plane of perspective, YOZ is a radio device a Projection plane of view, YOX is a radio device ab The projection plane of the view.

[0081] Step 105 , projecting the three-dimensional information of the target under multiple trajectories onto a reference coordinate system to obtain a three-dimensional image of the target.

[0082] In this step, for each trajectory, steps 101 to 104 are repeated to obtain the three-dimensional information of the target under each trajectory. That is, each trajectory can be calculated using two perspectives to obtain a three-dimensional image. Then, the three-dimensional information of the target under all trajectories is projected onto the reference coordinate system, and all the three-dimensional information is multiplied to obtain the three-dimensional image of the target under multiple perspectives (multiple angles) (if the perspectives are a , b , c, you can also use this method, for example, a , b The three-dimensional image and b , c If the viewing angles are a , b , c , d , you can choose a random combination, as long as all the perspectives are used, for example, a , b The three-dimensional image and b , c The three-dimensional image and c , d multiplying the three-dimensional image of ).

[0083] The above three-dimensional imaging method based on multi-angle trajectory has the following beneficial effects: 1) The importance of local area imaging is taken into account, allowing users to flexibly select the size of the imaging area according to the error curve to adapt to different application scenarios and accuracy requirements; in addition, a distributed radio equipment configuration is adopted, which is not restricted by fixed geometric shapes and can be arbitrarily configured according to actual needs, thereby providing greater flexibility and adaptability; through the selection of local areas and the deployment of distributed radio equipment, this method can significantly improve the imaging speed and efficiency while ensuring imaging accuracy, which is particularly important for application scenarios that require rapid response. For example, in the fields of emergency rescue, environmental monitoring or traffic management, fast and accurate three-dimensional imaging capabilities can greatly improve decision-making efficiency and response speed.

[0084] 2) Only two lines at any angle can be used for imaging, unlike the existing technology which requires at least a surface for imaging. This simplifies the imaging process and improves the imaging speed while ensuring the imaging quality, thus achieving fast data processing and imaging. It not only reduces the demand for computing resources and reduces computing costs, but also makes the entire imaging process more efficient, effectively solving the problems of low imaging speed and high cost in three-dimensional imaging. It has great application value and broad application prospects in actual engineering, and is particularly suitable for application scenarios that require real-time or near real-time feedback, such as rapid deployment and dynamic monitoring of drone swarms.

[0085] 3) The three-dimensional imaging method of this application is particularly suitable for drone swarms. The configuration of the drone swarm can be arbitrarily and flexibly configured according to the mission requirements. Whether it is a linear, grid-shaped or arbitrarily shaped flight formation, it can effectively collect three-dimensional data. The arbitrariness of this configuration provides great flexibility for the deployment of drone swarms, enabling them to adapt to various complex terrains and environmental conditions, while improving the coverage and efficiency of data collection.

[0086] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0087] In a specific embodiment, a simulation experiment is conducted, and the simulation parameters adopted are shown in Table 1.

[0088] Table 1: Simulation parameters

[0089] Radio equipment a , b The slant range-azimuth two-dimensional SAR image obtained by the viewing angle is expressed as follows Figure 6 , Figure 7 As shown. b From the perspective, the target's azimuth position is not at 300 meters. This is because a , b The angle between them is not 90°, so the target is b The azimuthal upward projection is:

[0090] in, , They are 300 meters and 0 meters respectively. Substituting them into the calculation, the b direction is 259.8076 meters, which is basically consistent with the result.

[0091] Using radio equipment a , b The angular relationship between the slant distance and the height obtained by the viewing angle , Get radio equipment a , b The height-azimuth two-dimensional SAR image obtained by viewing angle is as follows: Figure 8 , Fig. 9 As shown, it can be seen that the target altitude is basically at 10,800 meters, which is basically consistent with the actual position.

[0092] Fig.10 Radio equipment demonstrated a , bThe same height is obtained by slicing down through the basis transformation and translation transformation x - y From the directional two-dimensional SAR image, we can see that after basis transformation and axis shift operations, the target coordinates are basically consistent with the actual position, which verifies the validity of the above transformation matrix and translation matrix.

[0093] Fig.11 and Fig.12 The target 3D imaging result map is sliced ​​and analyzed. The theoretical resolution of the target in each direction is calculated as follows: The theoretical resolution of the direction is:

[0094] The theoretical resolution of the direction is:

[0095] The theoretical resolution of the direction is:

[0096] The actual resolution is Fig.13 , Fig.14 , Fig.15 As shown in the slice diagram, it is basically consistent with the theoretical resolution, which verifies the effectiveness of this method.

[0097] Introducing radio equipment c , in order to verify the improvement of imaging quality by multi-radio equipment and multi-angle. The target three-dimensional result is shown in the figure Fig.16 As shown, it can be seen that due to the radio equipment a , b , c The gain is much greater than that of radio equipment a , b , Fig.12 and Fig.16 Also in the case of -25db, Fig.16 The side lobes of the results are severely suppressed. Slice analysis of the above results is performed, such as Fig.17 , Fig.18 , Fig.19 The imaging quality indexes of the slices are better than Fig.12 .

[0098] The present application also provides a three-dimensional imaging device based on multi-angle trajectories, such as Fig. 20 As shown, in one embodiment, it includes: an acquisition module 2002, a conversion module 2004, an echo module 2006, a stacking module 2008 and a projection module 2010, wherein: The acquisition module 2002 is used to acquire a two-dimensional image of the radio equipment and obtain a slant range-azimuth two-dimensional SAR image of the target at different viewing angles of the current track by using a back-projection algorithm; The conversion module 2004 is used to obtain the angle between the radio device and the center slant distance of the imaging plane according to the center slant distance of the imaging plane at different viewing angles; and convert the slant range-azimuth two-dimensional SAR image into the altitude-azimuth two-dimensional SAR image according to the angle; The echo module 2006 is used to obtain the angles between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and the translation matrix, so as to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo; The stacking module 2008 is used to stack the echoes at the same height under different viewing angles of the radio equipment to obtain slices at the corresponding height; and to stack the slices at different heights to obtain the three-dimensional information of the target under the current track; The projection module 2010 is used to project the three-dimensional information of the target under multiple trajectories onto the reference coordinate system to obtain a three-dimensional image of the target.

[0099] For the specific definition of a three-dimensional imaging device based on multi-angle trajectories, please refer to the definition of a three-dimensional imaging method based on multi-angle trajectories above, which will not be repeated here. Each module in the above device can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0100] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0101] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A three-dimensional imaging method based on multi-angle trajectory, characterized in that: include: Acquire a two-dimensional image of the radio equipment and use a back-projection algorithm to obtain a two-dimensional SAR image of the target in slant range and azimuth at different viewing angles of the current trajectory; According to the imaging plane center slant distance at different viewing angles, the angle between the radio equipment and the imaging plane center slant distance is obtained; according to the angle, the slant range-azimuth two-dimensional SAR image is converted into an altitude-azimuth two-dimensional SAR image; Obtaining the angles between different radio devices and the reference coordinate axis, calculating the coordinate axis transformation matrix and the translation matrix, so as to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo; Take the echoes of the same height under different viewing angles of the radio equipment and stack them to obtain slices at the corresponding height; take slices at different heights and stack them to obtain the three-dimensional information of the target under the current trajectory; The three-dimensional information of the target under multiple trajectories is projected onto the reference coordinate system to obtain a three-dimensional image of the target.

2. A three-dimensional imaging method based on multi-angle trajectories according to claim 1, characterized in that: The slant range-azimuth 2D SAR image of the target at different viewing angles on the current track includes: In the formula, For radio equipment a Slant range-azimuth two-dimensional SAR image under viewing angle, for a The complex scattering coefficient under viewing angle, is the impulse response in the slant range direction, For radio equipment a Slant range coordinates under viewing angle, To target radio equipment a Slant distance under viewing angle, is the impulse response in azimuth, For radio equipment a The azimuth coordinates under the viewing angle, For radio equipment a The target position under the viewing angle, is an imaginary unit, is the wavelength of radio equipment; In the formula, For radio equipment b Slant range-azimuth two-dimensional SAR image under viewing angle, for b The complex scattering coefficient under viewing angle, For radio equipment b Slant range coordinates under viewing angle, To target radio equipment b Slant distance under viewing angle, For radio equipment b The azimuth coordinates under the viewing angle, For radio equipment b The target position in the viewing angle.

3. The three-dimensional imaging method based on multi-angle trajectory according to claim 2, characterized in that: According to the imaging plane center slant distance at different viewing angles, the angle between the radio equipment and the imaging plane center slant distance is obtained, including: In the formula, is the target height position, For radio equipment a The angle between the viewing angle and the slant distance from the center of the imaging plane, For radio equipment b The angle between the viewing angle and the slant distance from the center of the imaging plane.

4. The three-dimensional imaging method based on multi-angle trajectory according to claim 3, characterized in that: According to the angle, converting the slant range-azimuth two-dimensional SAR image into an altitude-azimuth two-dimensional SAR image includes: When the target meets the far-field condition: but: We can get: In the formula, is the error between the target height and the estimated value when the target is not in the center of the imaging plane, For radio equipment a Two-dimensional SAR image in altitude-azimuth direction under viewing angle, is the height coordinate, For radio equipment b Altitude-azimuth two-dimensional SAR image under viewing angle.

5. A three-dimensional imaging method based on multi-angle trajectories according to any one of claims 1 to 4, characterized in that: Obtain the angles between different radio equipment and the reference coordinate axis, calculate the coordinate axis transformation matrix and the translation matrix to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo, including: Obtain the angles between different radio devices and the reference coordinate axis, and calculate the coordinate axis transformation matrix according to the basis transformation principle; Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system; According to the coordinate axis transformation matrix and the translation matrix, the axis shift formula is used to transform the altitude-azimuth two-dimensional SAR image in the original coordinate system into the altitude-azimuth two-dimensional SAR image in the reference coordinate system, and the altitude-azimuth two-dimensional SAR image in the reference coordinate system is used as the echo.

6. The three-dimensional imaging method based on multi-angle trajectory according to claim 5, characterized in that: Obtain the angles between different radio devices and the reference coordinate axis, and calculate the coordinate axis transformation matrix based on the basis transformation principle, including: In the formula, is the axis transformation matrix, is the angle between different radio devices and the reference coordinate axis.

7. The three-dimensional imaging method based on multi-angle trajectory according to claim 6, characterized in that: Get the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system, including: In the formula, is the position of the image origin projected to the reference coordinate system, is the position of the target in the original coordinate system, is the position of the target in the reference coordinate system, is the translation matrix, Project the image origin to the reference coordinate system The position of the direction, is the image origin in the reference coordinate system The location of the direction.

8. A three-dimensional imaging method based on multi-angle trajectories according to any one of claims 1 to 4, characterized in that: The altitude-azimuth two-dimensional SAR image in the reference coordinate system includes: In the formula, For radio equipment a The reference coordinate system height-azimuth two-dimensional SAR image under the viewing angle, For Select the first indivual, is half of the total number of slices in height, For the A height slice, For radio equipment b Two-dimensional SAR image in the height-azimuth direction of the reference coordinate system under viewing angle.

9. The three-dimensional imaging method based on multi-angle trajectory according to claim 8, characterized in that: Take the echoes of the same height at different viewing angles of the radio equipment and stack them to obtain slices at the corresponding height, including: In the formula, is the slice at the corresponding height.

10. A three-dimensional imaging device based on multi-angle trajectory, characterized in that: include: An acquisition module is used to acquire a two-dimensional image of the radio equipment and use a back-projection algorithm to obtain a slant range-azimuth two-dimensional SAR image of the target at different viewing angles of the current trajectory; A conversion module is used to obtain the angle between the radio equipment and the center slant distance of the imaging plane according to the center slant distance of the imaging plane at different viewing angles; and convert the slant range-azimuth two-dimensional SAR image into an altitude-azimuth two-dimensional SAR image according to the angle; The echo module is used to obtain the angles between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and the translation matrix, so as to transform the height-azimuth two-dimensional SAR image in the original coordinate system into the height-azimuth two-dimensional SAR image in the reference coordinate system as the echo; The stacking module is used to stack the echoes at the same height under different viewing angles of the radio equipment to obtain slices at the corresponding height; and to stack slices at different heights to obtain the three-dimensional information of the target under the current track; The projection module is used to project the three-dimensional information of the target under multiple trajectories onto the reference coordinate system to obtain a three-dimensional image of the target.

Images